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Hawaiian Islands Synoptic Discussion and Guidance

097
FXHW60 PHFO 181330
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST THU SEP 18 2014

.SYNOPSIS...
WEAK HIGH PRESSURE NORTH OF THE AREA WILL KEEP LIGHT TRADES ACROSS
THE ISLANDS DURING THE NEXT FEW DAYS. SEABREEZES WILL DEVELOP WITH
CLOUDS AND SHOWERS RETURNING EACH AFTERNOON AND EVENING...ESPECIALLY
OVER LEEWARD AND INTERIOR AREAS. THE LIGHT WINDS WILL ALSO KEEP
GENERALLY WARM TEMPERATURES ACROSS THE AREA. INCREASING MOISTURE
SOUTH OF THE ISLANDS MAY BRING AN INCREASE IN RAINFALL OVER THE BIG
ISLAND LATE IN THE WEEKEND.

&&

.DISCUSSION...
WEAK SFC HIGH PRESSURE REMAINS LOCATED FAR N OF THE ALOHA
STATE...KEEPING WEAK TRADES ACROSS THE AREA THROUGH AT LEAST SAT. A
MID/UPPER LEVEL RIDGE IS ALSO LOCATED N OF THE ISLAND CHAIN. THIS
SYNOPTIC SCENARIO WILL ALLOW FOR MORE SEABREEZE CIRCULATIONS TO
DEVELOP EACH DAY...WITH PERIODS OF CLOUDS AND SHOWERS DURING THE
AFTERNOON AND EARLY EVENING HOURS.

MEANWHILE...MODELS REMAIN IN FAIR AGREEMENT REGARDING A COLD FRONT
PASSAGE ACROSS THE N CENTRAL PACIFIC DURING THE NEXT FEW DAYS. THIS
FRONT WILL FURTHER ERODE THE HIGH N OF THE ALOHA STATE AND ENHANCE
THE SEABREEZES. MOST THE RESULTING SHOWER ACTIVITY WILL INCLUDE
LEEWARD AND INTERIOR AREAS. THE LIGHT WINDS WILL ALSO ALLOW FOR
VOLCANIC HAZE TO BUILD AROUND THE BIG ISLAND...BUT SO FAR IT IS NOT
EXPECTED TO REACH THE SMALLER ISLANDS AS THE LIGHT WINDS SHOULD
STILL REMAIN GENERALLY FROM THE E.

FOR THE LONG RANGE FORECAST...MODELS SHOW A POSSIBLE TROPICAL
DISTURBANCE PASSING TO THE S OF THE ISLANDS BY SUN...BRINGING AN
INCREASE IN MOISTURE AND SHOWERS OVER THE BIG ISLAND. ALSO...THE
AFOREMENTIONED FRONT STALLS ABOUT A COUPLE HUNDRED MILES N OF THE
ALOHA STATE AND GRADUALLY DISSIPATES DURING THE WEEKEND. THE
PRESENCE OF
THE DECAYING FRONT TO THE N AND THE TROPICAL FEATURE TO THE S MAY
CAUSE AN INCREASE IN PRESSURE GRADIENTS ACROSS THE AREA WHICH IN
TURN COULD BRING AN INCREASE IN TRADE FLOW BY LATE SUN AND INTO MON.
REGARDLESS OF THIS SCENARIO...THE HIGH SHOULD BEGIN INTENSIFYING
EARLY NEXT WEEK WITH STRONGER TRADES RETURNING BY TUE/WED. THIS WILL
BRING BACK A TRADE WIND WEATHER PATTERN OF CLOUDS AND SHOWERS
FAVORING WINDWARD AND MOUNTAIN AREAS...ESPECIALLY AT NIGHT.

&&

.AVIATION...
BRIEF PERIODS OF MVFR CONDITIONS DUE TO REDUCED VIS IN SHRA AND
LOWER CEILINGS ASSOCIATED WITH LOW CLOUDS CARRIED BY LIGHT TRADE
WINDS MAY AFFECT SOME WINDWARD FACING SLOPES AND HIGHER TERRAIN.
LATER TODAY...THE LIGHT TRADE WINDS WILL ALLOW LOCAL SEA BREEZE
CIRCULATIONS DEVELOPING AGAIN ON EACH ISLAND FROM LATE THIS MORNING
THROUGH THIS AFTERNOON. EXPECT CLOUD BUILD UPS AND ISOL SHRA OVER
MOST LEEWARD AND INTERIOR SECTIONS OF THE ISLANDS THURSDAY AFTERNOON
AS A RESULT OF THE CONVERGENCE OF THESE SEA BREEZE CIRCULATIONS.

&&

.MARINE...
A PREVAILING MODERATE S SWELL WILL CONTINUE TO SLOWLY SUBSIDE THROUGH
FRIDAY. A SMALL LONG PERIOD SOUTH SWELL WILL KEEP SMALL SURF HEIGHTS
ALONG S FACING SHORES THROUGH THE WEEKEND.

A SMALL NW SWELL IS NOW ARRIVING...BUT SURF HEIGHTS OVER N FACING
SHORES ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS. NO OTHER MAJOR
SWELLS ARE IN THE FORECAST.

WINDS WILL REMAIN LIGHT THROUGH MOST OF THE FORECAST PERIOD. THE
TRADE WINDS WILL BEGIN INCREASING EARLY NEXT WEEK.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION/MARINE...REYNES
AVIATION...HOUSTON





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